Football fans who tuned in this weekend to see the New England Patriots break the all-time NFL record for consecutive wins also got a chance to see this year’s saddest team, the disintegrating Miami Dolphins. Each week brings a new and deeper embarrassment for a franchise that has not had a losing season since 1988.

The Dolphins have gone through running backs at roughly one a week, their two revolving quarterbacks have both been awful, their offensive line practically invites the opposing defense in for tea and crumpets, and they were reduced to having a backup wide receiver kick field goals this week.

Perhaps the strangest part of Miami’s lost season is that their defense has been as stalwart as ever. Only Denver has allowed fewer yards per game, and no team has been better at preventing third-down conversions. But even when you give up 17.8 points per game, you can’t win with an offense that scores less than 10 points per game.

While the Dolphins are the strongest example of a team that has been great on one side of the ball and terrible on the other side, they are not alone. It feels like more than ever the NFL is split between teams that can score at will but can’t stop anyone, and teams that can play defense but can’t score themselves. Only a few teams can play on both sides of the ball with any consistency.

If you have been noticing an increasing number of imbalanced NFL teams, your eyes do not deceive you. Going by the standard NFL ranking of yards per game, four teams rank in the top 10 in defense and the bottom 10 in offense: Tampa Bay, Washington, Baltimore, and Miami. Prior to this week, Jacksonville qualified as well, and Atlanta is close. Five other teams rank in the top 10 in offense and the bottom 10 in defense: Minnesota, Indianapolis, St. Louis, Houston, and (prior to last night’s game) Green Bay.

Does this lack of balance matter? Less than you might think. Since the league expanded to 30 teams in 1995, there have been 52 “unbalanced” teams, defined as instances where one unit ranks in the top 10 in yardage while the other unit ranks in the bottom 10.The total winning percentage of these teams was .494, and 38% of them made the playoffs, compared to 39% of other teams.

Once teams make it into the playoffs, however, lack of balance seems to be a problem. Four unbalanced teams have made it to the conference championships since 1995,but only one of those teams made a trip to the Super Bowl – the 2002 Buccaneers, who finished first in offense and 24th in defense.

The other three teams lost to opponents with far more balance. The 1995 Colts lost to the Steelers, top-six in both offense and defense. The 1999 Bucs fell to the Rams, top-three in both offense and defense. The 2000 Vikings fell to the Giants, who were 12th in offense and seventh in defense.

Watching this season’s games and highlights, it sure seems like there are more teams than usual playing well on just one side of the ball. But is this really the case? Based simply on raw yardage, there is nothing out of the ordinary about the large number of teams who early in the season find themselves strong on one side of the ball and weak on the other.

Last year after Week 5, there were 11 different teams that qualified as unbalanced. By year’s end, only three teams – Minnesota, Kansas City, and Buffalo – still had one unit ranked in the top 10 and the other in the bottom 10. In 2002, after Week 5, nine different teams qualified as unbalanced; at the end of the year, only five were still unbalanced.

The problem with these measurements, however, is that the NFL method of ranking teams simply by raw yardage has a number of flaws. It doesn’t take into account turnovers or red- zone efficiency, and it doesn’t consider the strength of schedule – an important factor since many unbalanced teams have faced similar unbalanced teams early in this season (for example, this week’s Houston-Minnesota shootout and Washington-Baltimore snoozefest).

A rating system I use at Football Outsiders, called DVOA, is a bit more complex than raw yardage. It judges each play during the season by comparing it to league-average performance based on situation and opponent, correcting for biases like garbage time and giving additional credit for red zone efficiency while penalizing teams for turnovers. Based on these ratings, the lack of balance that plagues so many teams this season has a much better chance of continuing for the rest of the year.

In 2002 and 2003, when lots of teams rated as unbalanced after five weeks based on yardage, only three or four teams rated as unbalanced based on DVOA – much closer to how teams played the entire season. This year, unlike in 2002 and 2003, DVOA says that the perceived lack of balance goes deeper than just raw yardage. Seven of the nine teams that rate as unbalanced according to yardage also rate as unbalanced according to DVOA. The exceptions are Green Bay and Tampa Bay, and the Bucs only miss because they are 11th in defense.

This result seems to match what we’ve seen in this year’s games. The teams that have great offenses and poor defenses haven’t let up yards when they lead late in games – they’ve been giving up yards all game long. And the teams that have great defenses and poor offenses have been unable to score even against the worst defenses on their schedules.

We can’t say for sure that the teams that have been all offense or all defense so far will stay that way for the rest of the year. But this year’s high number of unbalanced teams seems to be for real. Which means that, while poor defense probably won’t keep Indianapolis and Minnesota from winning seasons, it will probably keep them out of the Super Bowl yet again.

Mr. Schatz is editor in chief of FootballOutsiders.com